It has been known for some time that the yield of hydrocarbons, such as gas and petroleum, from wells can be increased by fracturing the formation so as to stimulate the flow of hydrocarbons in the well. Various formation fracturing procedures have been proposed and many now are in use. Among these procedures are treatments with various chemicals (usually acids in aqueous solutions), hydraulic fracturing in which liquids are injected under high pressure (usually with propping agents), explosive methods in which explosives are detonated within the formations to effect mechanical fracture, and combinations of the above procedures.
Chemical treatments usually involve the use of large volumes of chemicals which can be expensive and difficult to handle, and which pose problems of contamination and disposal. Hydraulic fracturing ordinarily requires that large volumes of liquids be made available at the well site and that equipment be made available for handling these large volumes of liquid. Again, there can be disposal problems, as well as contamination of the well. Explosive methods can be exceptionally hazardous from the standpoint of transporting and using the necessary explosives. These methods also present difficulties in controlling the effects of such a procedure.
Other suggestions for increasing the yield of existing wells entail heating the formation to induce the flow of hydrocarbons from the formation. Methods and apparatus have been developed by which various combustion devices have been lowered into the borehole of a well to attain heating of the formation adjacent the device. The effectiveness of such devices is limited by the necessity for fitting the devices into a borehole and then obtaining only more-or-less localized effects.
A combustion method designed to stimulate the well through mechanical fracture is known as controlled pulse fracturing or high energy gas fracturing. A good description of this method appears in an article by Cuderman, J. F., entitled "High Energy Gas Fracturing Development," Sandia National Laboratories, SAND 83-2137, October 1983. Using this method enables the multiple fracturing of a formation or reservoir in a radial manner which increases the possibility of contacting a natural fracture. Unfortunately, these radial fractures often do not penetrate deeply enough into the formation. Therefore, a method is needed which will extend the fractures deeper into the formation.
Sareen et al. in U.S. Pat. No. 3,896,879, disclose a method for increasing the permeability of a subterranean formation penetrated by at least one well which extends from the surface of the earth to the formation. This method comprises the injection of an aqueous hydrogen peroxide solution containing therein a stabilizing agent through said well into the subterranean formation. After injection, the solution diffuses into fractures of the formation surrounding the well. The stabilizing agent reacts with metal values in the formation which allows the hydrogen peroxide to decompose. Decomposition of hydrogen peroxide generates a gaseous medium causing additional fracturing of the formation.
Sareen et al. were seeking to enhance the radial propagation of the fracture into the formation around a wellbore. Also, Sareen et al. were seeking to provide a process for extending the fracture distance from the wellbore into the formation.
Using controlled pulse fracturing or high energy gas fracturing can generally cause multiple fracturing into the formation of about 50 to 75 feet. It is generally believed that using the method of Sareen et al. can cause fracturing into the formation of about 50 feet from the well or wellbore. However, this may be too optimistic as existing fractures may be too small to hold a volume of hydrogen peroxide sufficient to generate required fracturing pressure. Also some formations may not contain the metal values necessary to decompose the hydrogen peroxide. Often natural hydrocarbonaceous fluid fractures will occur at distances greater than 75 feet from the well or wellbore. Therefore, a method is needed to contact natural hydrocarbonaceous fluid fractures in those formations which have insufficient metal values to decompose hydrogen peroxide which occur at distances too far to be intersected or contacted with existing methods. Practicing the present invention allows the intersection or connection of natural hydrocarbonaceous fluid fractures at distances greater than heretofore possible while allowing hydrogen peroxide utilization in formations deficient in metal values.